(dailyRx News) Breast cancer doesn’t just strike older women. Although rare, girls as young as 15 have been diagnosed with this cancer. Unfortunately, it's well-known that the disease tends to be more lethal in young women than it is in older women. Scientists recently looked into what might be behind this phenomenon.

In a new study, those scientists concluded that the types of breast cancers adolescent and young adult women were diagnosed with had a great deal to do with their survival rates.

These subtypes are defined by the presence or absence of hormone receptors and the human epidermal growth factor (HER2) protein, all of which determine how and how quickly the cancer grows.

Race and ethnicity, along with socioeconomic and insurance status, also played a role in breast cancer mortality among young women, the study found.

"If you notice any breast changes, see your doctor."

Theresa H. Keegan, PhD, a researcher with the Cancer Prevention Institute of California in Fremont, CA, directed this investigation of the associations between breast cancer subtypes and short-term and breast cancer–specific survival in adolescent and young adult (AYA) patients.

Breast cancer accounts for 14 percent of all AYA cancers and 7 percent of all breast cancers diagnosed, the authors noted in the study's introduction.

For this study, the researchers used the California Cancer Registry to identify 5,331 AYA women diagnosed with breast cancer between 2005 and 2009. Socioeconomic and payment method information was gathered from hospitals, census and Social Security data.

The young women in this study were between the ages of 15 and 39, with the majority (62.5 percent) being in the 35-39 age group.

For comparison purposes, the researchers also followed 53,860 women between 40 and 64 years of age who also were diagnosed with breast cancer.

The research team examined the subtypes of breast cancer the participants had. These subtypes included the following:

Hormone receptor negative (HR-) breast cancers do not have these receptors.

HER2 positive (HER2+) breast cancer is defined by a high level of the HER2 protein, which makes the cancer very aggressive.

HER2 negative (HER2-) means the breast cancer cells do not have HER2 proteins.

Triple negative breast cancer has neither hormone receptors and does not have the HER2 protein.

The different subtypes of breast cancer define the presence or absence of the hormone receptors and the HER2 protein.

HR+/HER2- is breast cancer that has hormone receptors present, but not the HER2 protein.

HR+/HER2+ means both hormone receptors and the HER2 protein are present.

HR-/HER2+ has neither hormone receptors but has the HER2 protein.

Triple-negative negative has no hormone receptor or HER2 protein.

As is the case among all age groups, the most common type of breast cancer diagnosed in 41 percent of young women was HR+/HER2-. The next most common subtypes were triple-negative, which was found in 19 percent of the participants, and HR+/HER2+, which was identified in 15 percent of the women. These subtypes were followed by HR-/HER2+, which was seen in 8 percent of the study members.

After up to six years of follow-up, the study found that AYA women diagnosed with HR-/HER+ breast cancer had 1.6 times higher risk of dying than women with HR+/HER2- cancers.

Those with triple-negative breast cancer had a 2.7-fold increased risk of dying from the disease than did women with the more common HR+/HER2- type.

“Among AYA patients diagnosed with low-grade [not fast growing] tumors, the risk of breast cancer death was nearly fourteen-times higher in women with triple-negative and two-times higher in women with HR+/HER2+ compared to HR+/HER2- breast cancer,” the authors wrote.

The average survival among all of the women in the study was just over three years.

Overall, AYA women had a 44 percent higher risk of dying from breast cancer than women 40 to 64 years of age.

Black young women who lived in poorer neighborhoods and had public health insurance had worse survival than white participants.

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